While stuyding astronomy charts you don't want to ruin your night vision with those white lights so here is simple flashlight which will preserve your night vision.Our astronomy flashlight uses red LED's instead of white which will help you to preserve your night vision , it is rechargable and you can control the brigthness of the light according to your need.This is a simple and fun to do project.

This instructables explains how to create your own astronomy flashlight , test it and making some changes to it.

Step 1: Parts & Tools

Parts:
~ 5 x RedLED's - Local Electronics Store
~ BC635 Transistor - Local Electronics Store
~ 5.6 Ohm Resistor - Local Electronics Store
~ 270 Ohm Resistor - Local Electronics Store
~ NIMH Rechargeable Batteries(3.6v) - Got Mine From A Old Cordless Phone

Tools:
~ Soldering Iron - Sparkfun.com
~ Solder Wire - Sparkfun.com
~ Jumper Wires -Sparkfun.com
~ Protoboard - Sparkfun.com
~ A Small Container - I Found The Container At My Place

The cost would be around 5$ excluding the batteries and tools

Step 2: Build the Charging Circuit

Our flashlight can be recharged using the USB port of any Laptop Or PC.The circuit to achieve this is quiet simple it has only a single transistor and a few other components.The circuit relies on the fact that the current flow through a transistor is virtually the same in the collector as it is in the emitter.You can solder the circuit on a protoboard as I did or you could just do it without using anything.The LED in the circuit only lights up when the batteries are connected and charging.I have added the schematic (See last image)

Step 3: Building the LED Circuit & Putting It All Togather

For our LED circuit I have wired the LED's in parallel so that each and every LED gets enough voltage to light up as the power supply we are using is not adequate to light 4 LED's in series(They will be very dim).I have added a variable resistor for controlled brightness.Now to build the circuit first drill 4 holes in the cap of the container you have then fix 4 LED's into it and then wire them according to the circuit diagram(see Last Image) (Take a look at the pictures they really help).Drill a hole in the container for the variable resistor , USB port . I also have added a switch so that the flashlight can be eaisily switched on or off.Stuff all the thing in the container and colose the lid and you have your DIY Astonomy Flashlight.

Step 4: Testing

Now that we have made our flashlight lets test it.Put the switch in on position and all the LED's should up Turn the knob of the variable resistor and it should change the brightness of the LED's.Here we have completed the making and testing of our DIY Astonomy Flashlight

Step 5: All Done!

I hop that this project inspires further experimentation.Keep looking for better designs and improvement in the design for the flashlight.This is one of the few DIY rechargeable astronomy flashlight it is useful and easy to build.For any queries or suggestions leave a comment below ,send me a PM or E-Mail me at my E-Mail ID r1398ohit@gmail.com